Blackberry Cultivar Evaluation, Eastern Kentucky

Introduction

Blackberry (Rubus), a native plant, grows well in Kentucky, and new
improved blackberry cultivars offer a chance for crop diversification and a
high income per acre crop for Kentucky agricultural producers. Blackberries
have multiple uses including fresh or processed consumption, wine production,
and medicinal purposes. Rubus has lower establishment and labor costs
than many horticultural enterprises. It is also important to note that blackberries
have the potential to be grown on hilly land and strip-mine sites and have a
low erosion potential when grown in conjunction with sod strips. With available
mechanization, blackberries may be grown on a large scale and mechanically harvested,
or they may be grown on a small scale and hand-harvested for local fresh markets.

Materials and Methods

A thorny and thornless blackberry cultivars and advanced breeding selection
trial was planted in a randomized complete block experimental design in May
2000 on raised beds. For the thorny cultivars, six plants/replication were planted
2 ft apart in the row. The thornless erect cultivars were planted with four
plants/replication at a spacing of 3 ft. Plants of a thornless semi-erect cultivar
(Triple Crown) were planted 4 ft apart in the row with three plants per replication.
All rows were spaced 14 ft apart. There was a total of five replications with
a 3-ft space between replications. The blackberries received a single application
of 50 lb actual N/A from ammonium nitrate in March of 2001 and in 2002. The
blackberries were evaluated for vigor, winter/spring hardiness, disease problems,
as well as fruit yield, berry size, fruit appearance, and firmness.

Results

Many thorny and thornless blackberry cultivars have a tendency to de-harden
and break dormancy early in Quicksand where 60° to 70°F in January
and February are followed by 10° to 20°F in March and April. This
weather pattern occurs at least once every four or five years and did so in
2002. Thornless cultivars such as Hull and Triple Crown, while considered less
hardy than thorny blackberries, do very well here under our growing conditions
because they are slow to break bud and remain dormant later into the spring.
The year 2002 was a year of warm, sunny weather early and cold, overcast weather
late in the season. Table 1 shows the bloom development and the presence of
floricane injury in early May 2002. Canes showing injury at that time tended
to die prior to harvest, reducing yield and berry quality. Once hot, dry weather
came in June and July, a lot of floricanes were lost.

Table 1. Percentage of full bloom and floricane injury of 12 blackberry
cultivars and breeding selections evaluated on 4 May 2002 at Quicksand,
Kentucky.

Cultivar/

Selection*

Percent Full Bloom

Degree of

Floricane Injury

Comments

A1963

0

injured

3 of 5 replications injured

A1539

80

none

A2049

48

injured

3 of 5 replications injured

A1857

37

injured

2 of 5 replications injured

A1854

98

injured

1of 5 replications injured

A1960

15

injured

4 of 5 replications injured

A1689

1

slightly injured

1 of 5 replications injured

A1905

6

none

Navaho

1

severely injured

4 of 5 replications injured

Kiowa

5

none

double blossom

Shawnee

61

none

double blossom

Triple Crown

0

none

*

Selections preceded by an “A” and followed by a number are
unreleased breeding selections and are not available in commerce at this
time.

The three thorny blackberry cultivars tested are listed in Table 2. Kiowa produced
the highest yield (7,185 lb/A) and had the least amount of visible cane injury.
Unfortunately, Kiowa is very susceptible to a fungal disease called double blossom.
In a warm humid climate, it would be hard to raise Kiowa without having a good
fungicide spray program. Kiowa also has a tendency to lay down on the job, and
this makes picking and mowing difficult. A-1854 had tremendous fruit set, but
the injured floricanes in all five replications slowly declined, resulting in
small berry size. Shawnee was also subject to cane injury and had problems with
double blossom. In past trials at Quicksand, Shawnee had problems with hardiness
and disease and was included in this trial as a check for these problems.

Selections preceded by an “A” and followed by a number are
unreleased breeding selections and are not available in commerce at this
time.

1

The first day of harvest for that cultivar.

2

The number of days between first and last harvest for each cultivar.

3

Taste of fresh fruit, T = tart, S = sweet, B = bland.

4

A- = below average; A+ = above average; A = average.

5

SS = soluble solids of fresh berries.

6

Disease ratings are on a 0 to 5 scale; 0 = no disease seen, 5 = 100%
of plants have disease present.

7

Least significant difference at the 5% level.

The highest yielding thornless blackberry (Table 3) was Triple Crown (7,623
lb/A). The three cultivars A-1857, Navaho, and A-2049 all suffered severe floricane
injury and did not produce well. The fruit from Navaho were so small and dried
they were not marketable. The breeding selections A-1689 and A-1905 appeared
to suffer less cane injury and produced attractive fruit. The fruit quality
of these two selections made them the "pickers' choice" among all
the blackberries harvested this past year. No disease symptoms were observed
on any of the thornless blueberry cultivars. Additional tests are needed to
determine the long-term suitability of any blackberry cultivar to our climatic
conditions. Additional evaluations are planned for 2003.

Evaluation of Thornless Semi-Erect and Erect Blackberry Training Systems and
Varieties for Kentucky

Introduction

Blackberries continue to be a popular market item for Kentucky consumers,
and most growers find that high quality blackberries are readily marketable.
This study is being conducted as part of the New Crops Opportunities Fruit Project
at the Horticultural Research Farm in Lexington, Kentucky. One portion of the
study has been designed to evaluate two training systems for three thornless,
semi-erect blackberry varieties using a double-T four wire trellis. The second
portion of the study is to evaluate the use of a plastic bailing twine trellis
for cane stabilization versus no trellis for two thornless, erect blackberry
varieties.

Materials and Methods

Semi-erect thornless blackberry plants were set the spring of 2000 into black
plastic-mulched beds. Each plot consisted of three plants of either Hull Thornless,
Triple Crown, or Chester spaced 8 ft apart in the row with 12 ft between rows.
Each plot was replicated three times in a randomized block design. All plants
were trained on a double-T four-wire trellis with the lower two wires 2 ft apart
and the top two wires 4 ft apart. Two training systems were used, a conventional
system and the Oregon system.

In the conventional system, primocanes were topped when they had extended
1 ft above the top of the trellis. Dead fruiting canes that had cropped were
removed in the fall. During early spring, dormant pruning, spindly canes, and/or
those that had red-necked cane borer swellings were removed. Lateral branches
were pruned back to 18 inches in length, and those that were within 18 inches
of the ground were removed completely.

Primocanes were not summer tipped for the Oregon system. In the spring, canes
were not thinned, although those with red-necked cane borer swellings were removed.
Low laterals, within 18 inches of the ground, were removed. Laterals above this
were not cut back and were wound around, and sometimes loosely tied to the closest
trellis wire, extending away from the plant.

Arapaho and Apache erect blackberry plants were set 3 ft apart in the guard
rows on the north and south sides of the semi-erect blackberry plot. Trellising
treatments (supported and unsupported) and varieties were each replicated three
times in a completely randomized design. Plots consisted of three plants of
the same blackberry variety. Metal fence posts were set at intervals of 9 ft,
and plastic bailer twine was run on both sides of the supported treatment at
a height of 3.5 ft.

During the first (2000) growing season, canes were allowed to trail and grow
as much as possible. In the spring of 2001, the erect blackberry canes were
pruned severely to encourage development of more vigorous shoots for the following
season. During the summer of 2001 and 2002, primocanes were tipped at a height
of about 3 ft. Spindly canes and those with red-necked cane borer swellings
were removed in the spring of 2002. Laterals were cut back to a length of 16
to 18 inches.

The black plastic mulch was removed in the spring of 2001, and plants were
watered by hand as needed. The summer of 2002 was dry, and a trickle irrigation
system was installed. Plants were fertilized in February with calcium nitrate
at the rate of 8 lb/100 ft row (43.5 lb N/A). Weeds were controlled by hand
weeding, spot treatment with Roundup, and, in 2002, with Princep 4L. A conventional
fungicide spray program using Kocide, captan, Nova, and Benlate was maintained.
Japanese beetles and green June beetle pressure was severe in 2002, and both
sevin and malathion were used for control. Bird pressure was also severe early
in 2002, and an avian alarm was set up.

Plants were harvested in 2001 and 2002. Data were collected for yield, fruit
size, and fruit soluble solids. The season in 2002 was hot and dry, which helped
to elevate berry sugar content.

Results and Discussion

Statistical analysis was not conducted on the 2001 yield data (Table 1), but
trends for berry weight and soluble solids (% sugar) content were similar to
those obtained in 2002. Triple Crown tended to be the highest yielding and Hull
Thornless the lowest yielding in 2001, while this was reversed in 2002 (Table
2), although there was no significant difference in yield. The fruit load in
2001 could have been responsible for the reversal in 2002. Arapaho and Apache
had very low yields in 2001 due to the severe spring pruning.

Numbers followed by the same letter are not significantly different (Waller-Duncan
LSD P = 0.05).

In 2002, there were no significant differences in yield among the three semi-erect
blackberry varieties (Table 2) or between training systems (Table 3). Triple
Crown had a larger berry size than the other two varieties. Triple Crown berries
also had a 1% higher soluble solids (sugar) content than Chester, which in turn
had almost a 2% higher soluble solids content than Hull Thornless. The Triple
Crown fruit were noticeably sweeter than the other berries. Pickers felt that
Triple Crown had the most attractive-looking fruit.

Numbers followed by the same letter are not significantly different (Waller-Duncan
LSD P = 0.05).

Results for the erect blackberries can be found in Tables 4 and 5. Yields
were higher for the plants supported by the string trellis for both varieties
(Table 5), but there were no differences between training systems for average
berry weight or soluble solids. Berry weight was higher for Arapaho as compared
to Apache. This is contrary to the variety descriptions in the literature. There
were no differences between varieties for yield or soluble solids (Table 4).
Bird losses were more severe on the erect blackberries because these were the
first to ripen. Pickers felt that of the two thornless erect blackberries, Apache
had the more attractive fruit.

Introduction

A consumer demand analysis was completed during the summer of 2002 on fresh
blueberries grown in Kentucky. A very small acreage of blueberries (40 acres)
is currently in production, but a number of producers are looking at expanding
this enterprise. The demand analysis was conducted to provide market information
on consumer willingness to pay for various container sizes. Consumers were evaluated
in both a retail supermarket and a farmers' market. Product use, bulk purchase
capacity, and interest in pick-your-own were also explored. According to this
analysis, consumers in both small and big Kentucky towns are willing to pay
well above the grower breakeven price for fresh, high-quality Kentucky blueberries
in any size container.

Methodology

A random survey of 137 blueberry buyers was conducted during the first two
weeks of Kentucky's blueberry season. Most of the surveys (112) were collected
at the Lexington Farmers' Market. There were also 25 surveys collected in Metcalfe
County at the "Blueberry Festival" promotion that featured locally
grown blueberries in the Edmonton CB Foods grocery store.

The survey took less than two minutes to complete. It included questions about
how much consumers were willing to pay that day for retail blueberries, what
blueberries were being used for, whether the customer had freezer capacity,
and how much customers would be willing to pay for U-Pick blueberries.

Results and Discussion

Lexington Farmers' Market customers surveyed indicated that they would be
willing to pay an average of $3.14 per pint of blueberries in season (Table
1). Consumers at the Farmers' Market were accustomed to paying $3.00 per pint
for fresh blueberries. Most farmers' market customers, though, said that they
were willing to pay whatever the market price was for blueberries on any given
day.

Table 1. The MOST for blueberries that I would be willing to pay today.

Lexington

Average

Metcalfe County Average

½ pint is

$1.81

$1.17

1 pint is

$3.14

$2.08

1 quart is

$5.48

$3.83

In Metcalfe County, some 150 miles southwest of Lexington, CB Foods featured
local, handpicked blueberries for $1.88 per pint. CB Foods is a smaller retail
grocer that agreed to feature local blueberries in their produce section. The
consumers surveyed there on a Saturday indicated that they would be willing
to pay, on average, $2.08 per pint of blueberries (Table 1).

Customers at both the Lexington Farmers' Market and the Metcalfe County grocery
indicated that they would primarily use the blueberries purchased for fresh
fruit or baking (Table 2). Customers in the more rural Metcalfe County, though,
were more likely to have additional freezer capacity beyond a usual household
refrigerator (Table 3).

Table 2. My primary use for the blueberries that I am purchasing today.

Lexington

Metcalfe County

Baking (pies, muffins, etc.)

20%

50%

Fresh fruit (fruit salad, fresh ingredient)

88%

54%

Preserving (jam/jelly)

6%

8%

Other

2%

0%

Don’t know yet

0%

0%

Table 3. I use a free-standing freezer (deep-freeze) in my home.

Lexington

Metcalfe County

Yes

32%

85%

No

68%

15%

The additional amount that consumers would be willing to pay for a quart-size
container of blueberries over the pint-size was observed to be largest in the
farmers' market, an additional $2.34. This is 78% of the $3.00 price that customers
were used to paying at the farmers' market. The supermarket customers, however,
were willing to pay an additional 84%, or $3.83, of what they were used to paying
per pint for a quart-size container of blueberries (Table 1).

Wholesale prices for local berries at both these markets were well within
the $1.25 to $2.00 price per pint that Kentucky's blueberry farmers received
in 2002. Blueberry enterprise budget estimates from the UK New Crop Opportunities
Center show that blueberry growers can make adequate profits from blueberries
at these wholesale price levels. Growers who are willing to market their own
berries at "premium" markets (like the farmers' market) can expect
to generate significantly greater profits. Farmers' markets offer consistently
higher demand, but also have limited volume of product with fewer customers.

U-Pick Promise

Producers willing to tailor their production for U-Pick markets can often
capture higher profits than wholesale producers. This is because U-Pick eliminates
labor costs, the largest cost for wholesale blueberry production. In fact, according
to university estimates, those willing to develop a U-Pick blueberry market
in their area can make $800 to $1,500 more per acre over wholesale berry production
when charging a price of $1.25 per pint.

The survey indicated that about half the consumers at both markets would be
interested in picking their own berries at a nearby farm. Lexington Farmers'
Market customers said that they would pay an average of $2.13 per pint for berries
that they picked themselves (Table 4). Those surveyed at the Metcalfe County
grocery indicated that they would be willing to pay considerably less, $1.24
per pint, for U-Pick blueberries (Table 4).

Table 4. I would be interested in picking my own berries at a nearby
farm.

Lexington

Metcalfe County

Yes

58%

42%

No

42%

58%

$__/lb willing to pay for U-Pick

$2.13

$1.24

Interestingly, some of those surveyed at the Lexington Farmers' Market indicated
that they would be willing to pay more than they were paying at the market just
to go to a farm and pick their own berries. Therefore, enterprising farmers
willing to provide a hospitable and entertaining environment for U-Pick berry
customers may be able to capture additional profits.

Conclusion

Kentucky's blueberry acreage has doubled to 40 acres since 1997 and is expected
to double again to 80 acres by 2005. Statewide demand should easily support
this acreage increase. Furthermore, this survey indicates that consumers appear
to be willing to pay top price for fresh, high-quality Kentucky-grown blueberries.
This consumer willingness to pay top price for blueberries should ensure adequate
profits for those producers willing to invest the necessary time and capital
into this "new" crop for Kentucky.

A complete report of this survey is available online at www.uky.edu/ag/hortbiz.

Blueberry Cultivar TrialEastern Kentucky

Introduction

Although blueberries are a native fruit crop, only limited commercial acreage
has been established in Kentucky. Blueberries have an excellent potential for
local sales and U-pick operations. Recent research into the health benefits
of small fruits including blueberries may help increase sales even more. Vaccinium
is increasing in popularity in the world of pharmaceuticals. As consumers become
more conscious of the foods they eat, they may find themselves eating more blueberries.
Scientists attribute the blueberry's healing powers to the flavonoid anthocyanin,
which is responsible for the blue berry color found only in the peel. Anthocyanins
and other flavonoids could help fight the development of cancer, cardiovascular
disease, as well as eye problems such as glaucoma and poor night vision.

The high initial start-up costs for blueberries, approximately $4,000/A, is
mainly due to land preparation, plant, and labor costs. However, after the plants
reach maturity in approximately five years, the profits should steadily increase
to as high as $6,000/A per year. Farmers must make planting decisions based
on their own unique situation.

The longevity of a properly managed blueberry crop is similar to that of a
well-managed apple orchard. Blueberries require acidic soils with a pH of 4.5
to 5.2, with good drainage and high organic matter. It is best to plant more
than one cultivar to ensure good pollination and a continuous harvest of berries.
Harvest usually begins in early June and lasts well into July.

Materials and Methods

Two blueberry plantings were established in the fall of 1996 at the University
of Kentucky Robinson Station and the Laurel Fork Demonstration Site. Growth,
yield, and survival of various blueberry cultivars were compared between a normal
silt loam site and a disturbed mine site. The plantings consisted of 8 to 12
rows of various cultivars in a randomized block design. Plants were 4 ft apart
in raised beds 14 ft apart. Drip irrigation with point source emitters (2 gph/plant)
was installed shortly after planting. Plants were fertilized beginning in the
spring of 1997. In 2002 one application 5-20-20 (5 lb/100 ft of row) was followed
by two sidedressings of 5 lb ammonium sulfate/50 ft of row (at bloom and again
two weeks latter). Netting was used at both sites to prevent loss due to birds.

Results

Twenty-one cultivars at Quicksand and 18 cultivars at Laurel Fork were tested,
and results are shown in Tables 1 and 2, respectively. This year a cold, wet
spring with freezes during bloom (April 6 and 7) may have reduced yield. It
is believed that the flower buds of O'Neal, a southern highbush cultivar are
not hardy at these locations, and its yield has been very low. The early blooming
and maturing cultivar Duke has also continued to do poorly at both planting
sites. The Laurel Fork reclamation site is about 500 ft higher in elevation
than Quicksand and has much better air drainage. Moreover, based on time of
apple tree bloom, plant development at Laurel Fork is about seven to 10 days
behind that at Quicksand. As a result in both 2001 and 2002, the blueberry yields
were higher on the Laurel Fork disturbed soil site, and the plants had thicker
foliage and grew better. This is in contrast to the first harvest season where
Quicksand was the more productive site.

These cultivars are 1 year younger than the other cultivars in the trial.
Some cultivars were furnished by Hartman’s Plant Company, P.O. Box
100, Lacota, MI 49063. Other cultivars were purchased from Fall Creek
Farm & Nursery Inc., 39318 Jasper-Lowell Rd., Lowell, OR 97452.

1

In descending order of yield.

2

Means within a group followed by the same letter are not significantly
different, LSD (P = 0.05).

These cultivars are 1 year younger than the other cultivars in the trial.
Some cultivars were furnished by Hartman’s Plant Company, P.O. Box
100, Lacota, MI 49063. Other cultivars were purchased from Fall Creek
Farm & Nursery Inc., 39318 Jasper-Lowell Rd., Lowell, OR 97452.

1

In descending order of yield.

2

Means within a group followed by the same letter are not significantly
different, LSD (P = 0.05).

At Quicksand, Brigitta was again the highest yielding cultivar followed by
Blueray and Ozark Blue. Brigitta's yield was significantly higher than those
of the other 12 cultivars initially planted at Quicksand. Brigitta is an attractive,
large-fruited cultivar that matures in late mid-season in Kentucky with 82%
of the fruit picked during the first four harvests. Ozark Blue is another attractive,
medium to late maturing berry. Even though the Ozark Blue plants were a year
younger than the initially planted blueberry cultivars, it had the fourth highest
yield in 2002. Two North Carolina cultivars, NC-1832 and NC-1827, gave relatively
high yields at Quicksand. They had small to medium size berries with a pleasant
but distinctive taste. NC-1832 tends to flower heavily and set fruit in the
fall. Several other North Carolina numbered cultivars also appear to be later
maturing than the named cultivars in this trial. Plants of all five North Carolina
selections grew rapidly this past summer and are going to be much larger plants
than the named high bush cultivars. Late maturing blueberries in Kentucky will
require protective sprays to prevent damage by Japanese beetles.

At Laurel Fork, Bluecrop was the highest yielding blueberry (Table 2) followed
by Nelson, Bluejay, Blueray, and Toro. The largest berry sizes were those of
O'Neal, Toro, and Sierra. However, O'Neal had very few berries, which may have
resulted in larger average berry size. At Quicksand, Patriot and NC-2675 had
the largest berry size. Based on appearance, the most attractive blueberries
at Quicksand were Brigitta, Blueray, Ozark Blue, Toro, NC-2675, and Bluegold.
At Laurel Fork, Bluecrop, Nelson, Toro, Sierra, Duke, and NC-2852 were judged
to be the most attractive. At the Quicksand blueberry site, Jersey, Toro, and
Sierra have suffered some plant loss due to Phytophthora root rot. These results
represent the third harvest of these cultivars after 4½ to 5½ years'
growth. Additional harvests and observations will be needed to determine which
cultivars are the best performing over time in Kentucky.

Highbush Blueberry Cultivar TrialWestern Kentucky

Introduction

The blueberry is native to North America. At present, Kentucky has a small
acreage of commercial blueberry production. Blueberries have recently been touted
for their health benefits because of their high levels of antioxidants. Also,
highbush blueberries have been a good supplemental crop for Kentucky growers
who want to take advantage of land not suitable for tillage. For these reasons,
this study was initiated in order to evaluate highbush blueberry varieties for
adaptability to Kentucky soils and climatic conditions. This report updates
earlier results, presented in previous issues of the Fruit and Vegetable Research
Reports (1).

Materials and Methods

This trial, established in the spring of 1993 at the UK College of Agriculture
Research and Education Center (UKREC), in Princeton, Kentucky, consists of eight
cultivars spaced 4 ft apart within rows spaced 14 ft apart. There are 3 bushes
of each cultivar per replication. Prior to planting, the pH was reduced from
above 6.0 to 5.4 with elemental sulfur. The trial is mulched yearly with sawdust
and is trickle-irrigated using 1-gph vortex emitters. The trial is netted in
the last week of May, and fruit is harvested from the first week of June through
the first week of July.

Results and Discussion

Cumulative yield from 1995 through 2002, the 2002 yield, percent ripe fruit,
and berry size are presented in Table 1. Sierra, Duke, and Nelson cultivars
have yielded the most fruit to date. Duke and Sunrise are the earliest ripening
cultivars in this trial with 63% and 64% ripe fruit by the first week of June,
respectively. Relatively little harvesting is done for all other cultivars up
until the second week of June. Fruit harvest is finished for most cultivars
by the end of June. One exception is Nelson, which is picked throughout the
first week of July.

Another factor to be considered in selecting a cultivar is berry size (Table
1). Our data indicate that berry size can vary from the size of a pea to that
of a cherry. Typically, small berries are often preferred for cooking, while
larger ones are preferred for fresh consumption.

Finally, when selecting a cultivar for planting, growers should also consider
the difficulty of harvest. Blueberry pickers ranked the following cultivars
from easiest to hardest to pick: Toro, Duke, Sierra, Sunrise, Bluecrop, Bluegold,
Nelson, and Patriot.

These results should be useful to growers in selecting a blueberry cultivar.
Avoiding labor peaks and harvest times conflicting with the production and/or
harvest of other crops may have to be weighed against the highest yielding cultivar.

This article describes the results of the first seven harvests from this planting.
Other factors important to cultivar selection are discussed in other publications
(2, 3).

Pierce's Disease, a Disease of Grapes in Kentucky and Indiana

John Hartman, Claudia Cotton, Chris Smigell, and Julie Beale, Departments
of Plant Pathology and Horticulture and Hancock County Extension Office

Introduction

Pierce's disease, caused by the bacterium Xylella fastidiosa, is a
threat to grapes in California and in southern states from Florida to Texas.
Disease symptoms vary with species and cultivar, but are typified by marginal
browning of leaves and death of vines. This disease is favored by the warm winter
temperatures and long growing season found in the southeastern United States.
Last year, Pierce's disease was found for the first time in Kentucky (1, 2).

Symptoms of Pierce's Disease

Symptoms vary with the different species and cultivars. Symptoms in spring
and early summer include delayed shoot growth, leaf mottling, and dwarfing of
new shoots. Late summer and fall symptoms are more dramatic and include burning,
scorching, or drying of leaves; wilting or premature coloring of fruit; and
uneven cane maturity. Scorching begins near the margin of the leaf blade where
tissues become completely desiccated and die. As summer progresses into fall,
scorching progressively spreads inward in concentric zones until the entire
leaf blade is affected. Leaf blades often fall from the vine at the point of
attachment to the petiole, leaving the petiole still attached to the shoot.

The disease progresses along the grape vine with symptoms developing in adjacent
leaves along the shoot both above and below the point of initial infection.
Flower clusters on infected vines usually dry up. Late in the season, wood on
affected canes fails to mature normally, leaving green "islands" of
tissue that persist into the dormant season and can be seen on canes throughout
the winter. Tips of shoots often die the first year the vine is infected. Initially,
only one or a few canes on a vine show foliar and wood symptoms. Symptoms are
more pronounced in vines that are stressed by high temperatures and drought
conditions.

Grape Susceptibility and Disease Spread

Some grape cultivars are very susceptible, usually dying within two years.
Most French (vinifera) varieties die within two to five years, while
American (labrusca) varieties often live longer than five years. French-American
hybrids are intermediate in susceptibility. Pierce's disease is spread by several
types of sharpshooter leafhoppers, spittlebugs, and grafting.

For many years, trees, especially oaks, in Kentucky landscapes have suffered
from bacterial leaf scorch disease, also caused by X. fastidiosa but
a different strain from the one that causes Pierce's disease. Leaf scorching
symptoms associated with this disease annually appear in late summer. Symptoms
are quite striking on pin and red oaks, with individual leaves turning one-third
to two-thirds brown on the leaf ends and margins. The causal agent of bacterial
leaf scorch is also vectored by leafhoppers or other xylem-feeding insects.
As far as is known, the grape pathogen is the same species as the tree leaf
scorch pathogen, but is a different strain. Thus, the disease would not be spread
from trees to grapes.

The objective of this study was to begin a survey of vineyards in Kentucky
(and of one vineyard which we were called to in southern Indiana) to determine
where Pierce's disease was occurring.

Materials and Methods

Grape leaves showing leaf burning symptoms or dead areas on the leaf were
collected from vineyards statewide and in one southern Indiana county and delivered
to the UK Plant Disease Diagnostic Laboratory. Petioles from affected leaves
were crushed with a mortar and pestle so that the extract could be tested for
presence of the pathogen using a special laboratory test, an enzyme-linked immunosorbent
assay (ELISA) developed for X. fastidiosa ("Pathoscreen-Xf,"
Agdia Inc., Elkhart, Ind.). Color reactions for the ELISA test were evaluated
visually.

Results and Discussion

In all, 42 grape specimens from 13 vineyards were assayed in the laboratory.
They included the cultivars Chancellor, DeChaunac, Foch, Mars, Merlot, Riesling,
Vidal, and other cultivars, and also wild grapes where they were found near
the vineyard.

From these tests X. fastidiosa was detected in Mars grapes from Hancock
County and in Chancellor grapes from southern Indiana. Thus, although Pierce's
disease is not yet widespread in Kentucky, it is now confirmed still to be present
in Kentucky and is found for the first time in Indiana.

In the laboratory, we are developing a PCR test that we hope will tell whether
the grape strains of X. fastidiosa found here are the same or different
from X. fastidiosa in landscape trees in the region. This disease can
be devastating to grape production, and much more Kentucky research is needed.
Studies are also under way to determine which leafhopper vectors might be spreading
Pierce's disease in Kentucky. Where the disease is isolated, removal of infected
vines should keep further spread to a minimum.

With an emerging grape industry developing in Kentucky, it is important that
growers and County Extension Agents be on the lookout for this disease. Personnel
in the UK Plant Disease Diagnostic Laboratory can run the specialized tests
needed to determine the presence of the Pierce's disease bacterium.

Rootstock and Interstem Effects on Pome Fruit Trees

Introduction

Although apple is the principal tree fruit grown in Kentucky, the state's
hot, humid summers and heavy clay soils make apple production a more difficult
task for Kentucky growers than for growers in the major apple-producing regions
having more favorable conditions. The hot and humid summers are also a factor
in the high disease and insect pressure on orchards in Kentucky.

In spite of these challenges, productive orchards are one of the highest per-acre
income enterprises suitable for rolling hills and upland soil. Furthermore,
in these sites orchards have a low potential for soil erosion. Still, Kentucky
imports more apples than it produces.

Continued identification of improved rootstocks and cultivars is required
for growth of the Kentucky fruit industry. For this reason, Kentucky cooperates
with 39 other states and three Canadian provinces in the Cooperative Regional
NC-140 Project titled "Rootstocks and Interstem Effects on Pome Fruit."

The NC-140 trials are of utmost importance to Kentucky growers in terms of
gaining access to and testing new rootstocks from around the world. The detailed
and objective evaluation of these rootstocks provides growers with valuable
information needed to select the most appropriate rootstocks when they become
commercially available.

The 1994 and 1999 apple rootstock trials are designed to compare the adaptability
of the slender-spindle and the French vertical-axe systems in orchards grown
on our fertile soils. In addition, the semi-dwarf rootstocks in the 1999 apple
rootstock trial will provide information on the ability of these rootstocks
to support themselves without a trellis. The 2002 apple trial will provide us
with information on the differences in performance among clones of rootstocks.

The NC-140 orchard trials are used regularly as demonstration plots for visiting
fruit growers, Extension personnel, and research scientists. The research data
collected from these trials will help establish base-line production and economic
records for the various orchard system/rootstock combinations that can be utilized
later by Kentucky fruit growers.

Materials and Methods

Scions of known cultivars on various rootstocks were produced by commercial
nurseries and distributed to cooperators for each planting. The University of
Kentucky has three NC-140 rootstock plantings at the UK Research and Education
Center at Princeton (UKREC):

I. The 1994 apple rootstock trial consists of Red Gala on six rootstocks and
10 replications per rootstock. Trees are spaced 13 ft apart within rows 18 ft
apart. Trickle irrigation was installed, and a trellis system was constructed
in 1995.

II. The 1999 dwarf and semi-dwarf apple rootstock trial consists of two groups:

i) 11 dwarfing rootstocks with six replications per rootstock. Trees are planted
on a 10-ft by 16-ft spacing.

ii) six semi-dwarfing rootstocks with six replications per rootstock. Trees
are planted on a 13-ft by 20-ft spacing.

The experimental field is laid out as a randomized block design. Orchard floor
management consisted of a 6.5-ft herbicide strip with mowed sod alleyways.

Trees were fertilized and sprayed according to local recommendations (1, 2).
Yield, trunk circumference, and maturity indices were measured.

Results and Discussion

The winter of 2002 was mild, followed by a wet spring and below-normal rainfall
from June through August. Summer temperatures were above normal. Rainfall was
moderate to above normal throughout the remainder of the growing season. An
early spring hailstorm severely damaged the fruit in the 1999 NC-140 trial.
Several trees were also blown over.

I. 1994 Apple Semi-Dwarf Rootstock Trial

This is the first orchard trained to the French vertical-axe system at this
station. It includes a number of new rootstocks, along with others that have
performed well in previous trials at this location.

Survival of trees on M.26 EMLA rootstock (10% survival) differed significantly
from trees on the other three rootstocks (90% survival). Cumulative yield, yield
in the year 2002, trunk cross-sectional area, fruit size, flesh firmness, and
number of root suckers varied significantly among rootstocks (Table 1). No significant
differences were observed for percent soluble solids (data not shown). Trees
on CG.30 and V.2 rootstocks have been the most productive in this trial. On
the other hand, trees on B.9 rootstocks have been the least productive.

II. 1999 Dwarf and Semi-Dwarf Apple Rootstock Trial

This trial consists of two groups of apple rootstocks, a dwarfing group with
11 rootstocks, and a semi-dwarfing one with six rootstocks. Eight of the dwarfing
and three of the semi-dwarfing rootstocks had not been tested previously at
UKREC. At planting time, we received 90 trees of a possible 102 for this trial
because 12 trees were not available for our site (one each of G.16N, CG.6814,
and CG.5202, two CG.4013, three CG.3041, and four CG.30N). Furthermore, three
trees never leafed out after planting (one G.16T, one G.16N, and one CG.3041).
Five trees in the dwarf planting (one each of CG.5179, G.16N, G.16T, and two
of CG.5202) and seven trees in the semi-dwarf planting (one each of CG.6814
and M.26, two CG.7707, and three Supporter 4) broke off at either the roots
or the graft union this summer. No statistical differences in mortality were
observed among the rootstocks for either group.

For both groups, significant differences were observed for trunk cross-sectional
areas, yield in 2002, and cumulative yield (Table 2). The number of root suckers,
flesh firmness, and the percent soluble solids varied significantly only among
the dwarf rootstocks. Average fruit weight did not vary significantly by rootstock
for either the dwarf or semi-dwarf group. Twenty-two of the 31 semi-dwarf trees
planted are now supported by tree stakes due to their lean exceeding 30°
from vertical. Some of these trees have blown over, breaking at the roots or
at the graft union.

Table 2. Results of the year 2002 for the NC-140 1999 apple dwarf and
semi-dwarf rootstock trial, UKREC, Princeton, Kentucky.

Rootstock

Cumulative

Yield

(lb/tree)

2002

Yield

(lb/tree)

Trunk

Cross-Sectional

Area (in.2)

Number

of Root

Suckers

Flesh

Firmness

(lb)

Percent

Soluble

Solids

Fruit

Weight

(oz)

Dwarfing*

CG.4013

89.9

64.4

5.3

14.0

20.3

13.7

5.0

G.16T

80.9

57.1

4.2

1.8

20.5

14.1

4.8

CG.5202

67.5

62.6

4.1

8.3

20.3

13.3

5.0

G.16N

64.2

37.5

29.0

2.3

22.5

14.1

5.1

M.9 NAKBT 337

57.8

48.9

16.8

2.8

20.1

13.3

5.5

Supporter 2

54.2

33.7

20.1

0.3

20.9

13.7

5.0

M.26 EMLA

51.1

46.5

18.7

1.7

19.8

13.6

5.4

Supporter 3

50.9

23.8

18.9

2.0

23.1

15.2

4.8

CG.5179

48.3

41.0

20.5

2.4

20.3

14.1

4.8

Supporter 1

47.2

23.4

19.7

3.7

22.9

14.6

4.8

CG.3041

31.7

13.4

26.7

0.5

22.5

11.7

5.6

Average

58.4

41.0

22.4

3.3

20.9

13.9

5.0

LSD (5%)

20.5

26.5

5.9

5.9

2.4

1.5

NS

Semi-Dwarfing*

CG.30N

66.1

48.9

5.2

5.5

20.9

12.8

6.2

CG.4814

60.0

58.4

4.0

9.3

20.3

14.6

5.5

M.26 EMLA

34.8

24.7

3.2

0.4

21.4

14.5

5.9

CG.7707

31.7

29.5

5.7

4.8

21.2

14.1

5.8

M.7 EMLA

28.0

20.1

5.1

25.2

21.4

15.0

5.4

Supporter 4

23.4

12.1

2.7

9.3

23.6

16.1

4.9

Average

37.9

30.4

4.3

10.3

21.4

14.6

5.6

LSD (5%)

26.9

24.3

1.9

NS

NS

NS

NS

*

Within groups, arranged in descending order by cumulative yield.

III. 2002 Apple Rootstock Trial

This trial compares nine rootstocks consisting of three clones of M.9, two
clones each of B.9 and M.26, and one clone each of Supporter 4 and of P.14.
Sixty-three trees of Buckeye Gala, nine different rootstocks and seven replications
per rootstock, were planted in a randomized complete block design in a block
of seven rows with a pollenizer tree at the ends of each row. A trellis was
constructed and trickle irrigation installed a month after planting. To date,
all trees are alive and growing vigorously.

Significant differences were observed for both spring and fall trunk cross-sectional
areas and for the change in trunk cross-sectional area from spring to fall.
No differences were observed in number of feathers or number of suckers (Table
3).

Optimal Training of Apple Trees for High Density Plantings

Introduction

Kentucky apple growers often have a problem with excessive vegetative growth
or vigor of their trees, which greatly reduces the production that can be achieved
from high density apple plantings. Early production and optimal fruit size on
vigorous sites are obtained when photosynthates are balanced properly between
flower bud initiation and vegetative growth. Pruning and training are possibly
the most important operations performed by growers to maintain the proper balance
between flower bud initiation and vegetative growth. Identification of effective
pruning and training techniques for vigorous sites is required for continued
expansion of apple production in Kentucky. The University of Kentucky College
of Agriculture (UK) and the Kentucky State Horticultural Society (KSHS) have
made long-term commitments to help meet this need and are cooperating in this
ongoing research, the purpose of which is to determine the best training and
pruning practices needed to obtain early production and optimal fruit size from
trees trained to the slender-spindle or the French vertical-axe system.

Materials and Methods

One hundred-sixty trees of Golden Delicious on M.9 rootstocks were planted
in May 1997 in a randomized complete block design consisting of five rows and
32 trees per row. At planting, trunk circumference at 12 inches above the soil
surface averaged 2.4 inches and did not vary significantly among rootstocks.
A trellis was constructed, and trickle irrigation was installed. Trees were
spaced 8 ft apart within rows 16.4 ft apart. Orchard floor management was a
6.5-ft herbicide strip with mowed sod alleyways. Trees were fertilized and sprayed
according to local recommendations (1, 2). Beginning in 1998, yield, trunk circumference,
and maturity indices such as soluble solids and flesh firmness were measured
after harvest.

The trees were trained according to detailed treatment protocols presented
in Table 1. Trees began to fill their allotted space in 1999, and leader management
was modified to maintain leaders at specified heights (Table 1). Limbs of one
tree that overlapped or touched those of adjacent trees were headed back to
two-year-old wood.

French Axe: remove overly vigorous branches with narrow angles when 3
to 6 inches long. Slender Spindle: remove branches that compete with leader.
In 2000, for both training systems, limbs overlapping or touching those
of adjacent trees were headed back into 2-year-old wood.

Leaders were maintained at specified heights (ft) by cutting to an alternate
leader when necessary. Y = Alternate leader was bent to horizontal for
6 weeks. Z = Alternate leader was “snaked” throughout growing
season. Leader management was the same in 2002 as in 2000 and 2001.

Results and Discussion

No significant differences were observed between the French vertical-axe and
the slender-spindle training systems for any of the measured variables. Therefore,
all data are presented as the combined values for both systems. No differences
among the four pruning levels were observed for cumulative yield (1998-2002),
yield in 2002, fruit weight, and trunk circumference (Table 2).

Table 2. Effects of pruning and training treatments on yields of the
1997 apple training study at UKREC, Princeton, Kentucky.

Starting in 2000, the pruning protocol was changed to once early in the
season for all treatments.

3

Yield is the sum of picked and dropped fruit. Dropped fruit averaged
9.1 lb/tree in 2002.

Pruning time per tree was not analyzed statistically; thus, no LSD values are
presented in Table 3. Even though pruning time per tree appears to be the highest
for the heavy pruning level, this difference was not significant to the pruning
crew. Pruning time, when adjusted for pounds of fruit produced, did not differ
among the four treatments (Table 3). Total pruning and training periods were
14 weeks in 1997, 12 weeks in 1998, 18 weeks in 1999, four weeks in 2000, four
weeks in 2001, and one week in 2002.

Table 3. Time required for pruning and training of the 1997 apple training
study at UKREC, Princeton, Kentucky.

Starting in 2000, the pruning protocol was changed to once early in the
season for all treatments.

This planting has been regularly used as a demonstration for visiting apple
growers, Extension personnel, and research scientists. The data collected in
these trials have helped establish baseline economics and production methods
for the various orchard system/rootstock combinations that can be utilized by
Kentucky fruit growers.